Copper base alloys are known which contain relatively large amounts of nickel and manganese. Alloys of this type are highly desirable since they are capable of obtaining high yield strengths upon aging. U.S. Pat. No. 3,712,837 discloses processing such alloys in order to obtain good yield strengths upon aging and good stress corrosion resistance.
The copper-nickel-manganese age hardenable alloys have suffered from inadequate stress corrosion resistance, which has severely limited the applications where they can be used. Parts manufactured from these alloys may be susceptible to stress corrosion cracking when exposed to the atmosphere or an accelerated stress corrosion cracking test environment. Stress corrosion cracking can be a serious problem in any formed part, such as springs, lock parts and the like.
Accordingly, it is a principal object of the present invention to provide a process which is capable of greatly improving the stress corrosion resistance of the nickel and manganese containing copper base alloys.
It is a further object of the present invention to provide a process as aforesaid which is simple and convenient to use on a commercial scale.
Further objects and advantages of the present invention will appear hereinafter.